This invention relates to the incorporation of terpene into molten LLDPE for achieving animal repellent articles formed from the resultant melt.
French Patent 2,542,002 (1984) discloses the incorporation of terpene into a wide variety of thermoplastic and thermosetting polymers for the purpose of modifying the olfactory effect of the polymer so as to have a repulsive effect on animals. Various amounts of terpene additive are disclosed, i.e. 0.01 to 5% by wt., and most frequently between 0.1 and 2%. In order to mask the strong odor of products in a package (case) made from the polymer, the best percentages of terpineol is in the range of 0.5 to 1.5 % of the weight of the package. Example 1 discloses the manufacture of trash bags from LDPE, in which 1% by weight of a mixture of terpineol and heavy terpene was added to low density polyethylene (LDPE) molding granules for extrusion into film which is fabricated into trash bags. The resultant trash bags are disclosed to be filled with odorous foodstuff and they were observed not to be attacked by dogs, cats and rats, whereas trash bags made from the LDPE without the terpene additive were observed to be attacked by the animals.
Unfortunately, the trash bags of Example 1 of the French patent have insufficient shelf life to be of practical utility. The volatility of the terpene additive in the LDPE rapidly decreases the amount of terpene present in the trash bag until it is no longer effective. The amount of terpene added in Example 1 of the patent appears to have been limited so as not to cause any defect in the film formed from the terpene/LDPE mixture. Another limitation on terpene amount would be to avoid excess terpene which would have an offensive odor to humans or would provide an offensive oily appearance to the film.
U.S. Pat. No. 4,320,112 discloses animal and insect repellent trash bags in which the combination of naphthalene flakes and oil of citronella in solid form is added to a synthetic resin forming the bags. The patent discloses that each component of the combination is insect repellent and that the combination provides animal repellency as well. The patent also discloses that the weight proportion of naphthalene to oil of citronella is at least 4:1. The use of these additives in solid form inevitably weakens the bag because there is no compatibility between the resin and these additives, whereby they form weak spots for the development and propagation of tears in the film forming the trash bag. Thicker films can compensate for this deficiency, to provide for the strength needed by trash bags made from the film, but this is uneconomical.